'Twincretin' Beats Glargine for Diabetes in Pivotal Trial

Mitchel L. Zoler, PhD

October 28, 2021

The "twincretin" tirzepatide scored another pivotal-trial win in full, published results from the multicenter SURPASS-4 trial, which compared the investigational agent to insulin glargine for treatment of type 2 diabetes. The study comprised 1,995 randomized patients with inadequately controlled type 2 diabetes and high cardiovascular disease risk.

Positive results for tirzepatide from SURPASS-4, the fifth and final registration trial for the drug, as well as in the other four studies, tee up the agent for a planned approval submission to the Food and Drug Administration by the end of 2021.

SURPASS-4 differed from the four other pivotal trials not only in its comparator agent, but also by being the longest of the five and the only one that, by design, enrolled exclusively patients with either established cardiovascular disease or high risk for the disease.

The new results "provide initial support for glycemic control [by tirzepatide] being sustained for more than 1 year," wrote Stefano Del Prato, MD, and associates in their published report in The Lancet.

Despite the trial's primary endpoint of change in hemoglobin A1c after 52 weeks on treatment, the study continued for another year and had a median time on treatment of 85 weeks, with 7% of enrolled patients remaining on treatment for the maximum on-treatment follow-up of 104 weeks.

Potent Glycemic Control

The primary endpoint showed that treatment with tirzepatide produced an average incremental reduction in A1c of 0.99% among 328 patients treated with a 10 mg weekly subcutaneous dosage compared with the 1,000 patients who received insulin glargine (Basaglar, Lantus, Toujeo), and an average 1.14% incremental reduction in A1c among 338 patients on a 15-mg dosage once weekly, reported Del Prato, professor and chief of the section of diabetes at the University of Pisa (Italy).

This met the prespecified criteria for noninferiority of tirzepatide to insulin glargine for reduction of A1c, the study's primary objective, and also met the study's prespecified definition of superiority, both statistically significant results. The study also tested a weekly tirzepatide dosage of 5 mg that was significantly superior to insulin glargine for glycemic control.

"The magnitude of A1c reduction and the proportions of patients reaching glycemic targets appear to be larger than in similar studies in which GLP-1 [glucagon-like peptide–1] receptor agonists have been compared with glargine," the investigators wrote in their report.

The A1c effect of tirzepatide seen across all five SURPASS trials "surpasses what we've seen with other [glycemia control] drugs, with the possible exception of insulin," said Jan W. Eriksson, MD, PhD, professor of clinical diabetes and metabolism at Uppsala (Sweden) University.

The results also showed several other clinically meaningful benefits from tirzepatide treatment. A composite outcome of reduction of A1c to less than 7% with no weight gain and no clinically significant documented symptomatic or severe hypoglycemia occurred in 74%-88% of patients in the three tirzepatide arms compared with 13% of patients treated with insulin glargine. After 52 weeks on treatment, body weight fell by an average of 8%, 11%, and 13% from baseline in the three tirzepatide treatment arms in a dose-dependent way, while weight rose by an average of 2% among those who received insulin glargine. Weight reduction of at least 10% occurred in 36%-66% of patients treated with tirzepatide, compared with 2% on treatment with insulin glargine.

SURPASS-4 was not run as a blinded study because of differences in administration of the comparator agents.

Safety Appears Similar to GLP-1 Receptor Agonists

The safety profile of tirzepatide in SURPASS-4, as it was in all of the other four trials in the SURPASS series, was consistent with previously reported safety of agents in the GLP-1 receptor agonist class, said Del Prato. It was an expected finding as tirzepatide combines activity as a GLP-1 receptor agonist with activity as a glucose-dependent insulinotropic polypeptide (GIP) receptor agonist in a single molecule.

The most common adverse effects were gastrointestinal, including diarrhea, nausea, decreased appetite, and vomiting. Most of these effects were mild or moderate, and they occurred most often during dose escalation of tirzepatide in the first 24 weeks on treatment.

The GIP receptor agonist effect of tirzepatide may diminish the nausea experienced by patients as a result of the drug's GLP-1 receptor agonist action, Eriksson, designated discussant for the SURPASS trials, said during a session Sept. 30 at the virtual annual meeting of the European Association for the Study of Diabetes (EASD).

Clinically significant or severe hypoglycemia occurred in 8% of all patients on tirzepatide, with no apparent dose relationship, about half the rate of the patients treated with insulin glargine. Notably, the hypoglycemia episodes among patients treated with tirzepatide clustered almost entirely in the subgroup of patients who also took a sulfonylurea agent during the study. (SURPASS-4 allowed enrolled patients to be on their background antidiabetes regimen throughout the study, and at baseline 95% were taking metformin, 54% were on a sulfonylurea, and about a quarter were on a sodium-glucose cotransporter-2 inhibitor.)

"I would advise not using tirzepatide with insulin or with a sulfonylurea," Eriksson said. Aside from this risk for hypoglycemia when tirzepatide is used concurrently with certain other antidiabetes drugs, the SURPASS trials have shown "no other important safety signals," Eriksson added.

Cardiovascular Safety

All enrolled patients had either known coronary, cerebrovascular, or peripheral arterial disease or were at high risk for having one or more of these conditions because they were at least 50 years old with a history of either chronic kidney disease with depressed glomerular filtration or heart failure.

During complete follow-up, the composite rate of cardiovascular death, MI, stroke, or hospitalization for unstable angina was numerically less in the patients who received tirzepatide, 5%, than in those on insulin glargine, 6%, a 26% relative risk reduction that did not achieve significance. The rate of total mortality was 3% in the tirzepatide group and 4% among those on glargine, a 30% relative risk reduction that was not significant.

The cardiovascular disease outcomes "suggest that tirzepatide is safe from a cardiovascular perspective," Del Prato said when he presented the SURPASS-4 results during the virtual annual meeting of the EASD. However, a much larger cardiovascular outcomes trial of tirzepatide, SURPASS-CVOT, with more than 12,000 randomized patients and using a GLP-1 receptor agonist as the comparator, is now in progress, with a report on the findings expected in 2025.

Overall, results from all five SURPASS trials of tirzepatide have shown that the drug is "effective and safe in people with type 2 diabetes, providing stringent glycemic control and additional metabolic benefits including weight reduction and an improvement in other cardiometabolic markers," said Melanie J. Davies, MD, professor of diabetes medicine at the University of Leicester, England.

Looking forward to when tirzepatide will be available for routine use, Eriksson positioned it near-term as part of a dual or triple regimen, especially for patients with type 2 diabetes who are obese or have uncontrolled hyperglycemia, renal impairment, high cardiovascular disease risk, or high risk for clinically significant or severe hypoglycemia. A role for tirzepatide as a first-line agent is currently "more speculative," he added, with more data needed on cardiovascular outcomes, long-term safety, and cost effectiveness.

The existing evidence base for tirzepatide shows "very promising efficacy" for weight loss and glucose lowering with "reassuring safety and tolerability," and is a "very important addition to current options," although the long-term safety of chronic tirzepatide treatment remains unproven, he said.

Eriksson called the drug's glycemic control "strong and durable" based on the entire SURPASS program, with a "major" weight loss effect. He also suggested that while the adverse effect profile of tirzepatide appears similar to the GLP-1 receptor agonists, the incidence of gastrointestinal adverse events may be lower with tirzepatide.

SURPASS-4 and the other SURPASS trials were funded by Lilly, the company developing tirzepatide. Del Prato has ties with Lilly, Applied Therapeutics, AstraZeneca, Boehringer Ingelheim, Merck Sharpe and Dohme, Novartis, Novo Nordisk, and Sanofi. Davies has ties with Lilly, AstraZeneca, Boehringer Ingelheim, Janssen, Merck Sharp & Dohme, Novo Nordisk, Sanofi-Aventis, Servier, Gilead Sciences, Napp Pharmaceuticals, Mitsubishi Tanabe, and Takeda. Eriksson has ties with AstraZeneca, Ilya Pharma, Merck Sharp & Dohme, and Novo Nordisk.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.


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